Photographic intensification process and composition

ABSTRACT

A PHYSICAL DEVELOPER FOR LATENT IMAGES IN SILVER SENSITIZED PHOTOGRAPHIC MATERIALS COMPRISES A CUPRIC SALT AND A REDUCING AGENT SUCH AS ASCORBIC ACID FOR THIS CUPRIC SALT. A SILVER SALT SOLVENT TRANSFER DEVELOPER ALSO CONTAINS A SILVER HALIDE SOLVENT. LATENT IMAGE NUCLEI ARE PHYSICALLY DEVELOPED OR INTENSIFIED BY THE CUPRIC SALT PHYSICAL DEVELOPER.

United States Patent 3,730,721 PHOTOGRAPHIC INTENSIFICATION PROCESS AND COMPOSITION John Williams and Paul Gilman, Rochester, N.Y., assignors to Eastman KodakCompany, Rochester, N.Y. ,No Drawing. Filed Oct. 22, 1965, Ser. No. 502,389 Int. Cl. G030 5/24, 5/26, 5/32 U.S. CI. 96-48 PD 32 Claims ABSTRACT OF THE DISCLOSURE A physical developer for latent images in silver sensitized photographic materials comprises a cupric salt and a reducing agent such as ascorbic acid for this onpric salt. A silver salt solvent transfer developer also contains a silver halide solvent. Latent image nuclei are physically developed or intensified by the cupric salt physical developer.

This invention relates to a novel method for preparing photographically useful images by physical or chemical development of latent image specks or nuclei, produced in an imagewise pattern by an exposure to light, using developing solutions comprising a soluble copper salt and an appropriate reducing agent whereby metallic copper in visible amounts is selectively deposited on the image specks or nuclei.

It is well known that a solution of silver ion in combination with a reducing agent can be used to physically develop latent image specks or nuclei which remain after exposing and fixing an emulsion layer of silver halide. For example, a physical developer frequently used comprises an aqueous solution containing silver nitrate and a reducing agent such as hydroquinone, Elon, p-phenylenediamine, and the like. For further details of processes of this kind, reference can be had to The Theory of the Photographic Process, by CJE. K. Mees, revised edition, pp. 747-750, The MacMillan Company, New York. While such silver ion containing physical developers have in many cases produced fairly satisfactory latent image intensifications, the use thereof has been somewhat lim ited because of, the inherent instability and greater cost of these developing solutions. Also, where warmer image tones are desired, an additional toning step is usually necessary.

We have now made the important discovery that various photoproduced latent images can be intensified or developed in a very rapid, eifective and economic manner, to give developed images of controlled density and desired tone, by the use of a physical and chemical developer comprising a solution of a soluble-cupric salt and a suitable reducing agent. Metallic copper is thereby selectively ,deposited in the exposed regions. An especially useful developer of the invention comprises .an aqueous solution of cupric nitrate and ascorbic acid or its alkali metal salts. Many of the so-called electroless copper plating solutions or baths are also operable in the process of the invention, but are usually less desirable for one reason or another, but principally because of their prolonging the developing time. Such solutions are described in a number of publications represented, for example, by ffElectroless Plating of Metals by Chemical Reduction, Natl. Bur. of Standards, Tech. Bull, 31, 111 (1957).

It is, accordingly, an object of the invention to provide a novel process of intensification or development of various photoproduced latent images in photographic layers by treating the layers with a physical and chemical developer comprising a solution of a soluble cupric salt and an appropriate reducing agent whereby metallic copper is selectively deposited in the exposed regions.

Anotherobject is to provide a process of the above kind wherein the physical and chemical developer comprises an aqueous solution of cupric nitrate and ascorbic acid. Another object is to provide a novel process of the above kind wherein a silver, zinc or lead type of latent image is intensified or developed. Another object is to provide a novel solvent transfer method of intensification or development of latent images using copper developers of the invention containing in addition a solvent for silver halide. Another object is to provide novel photographic products having intensified or developed visible images produced in accordance with the above processes of the invention. Another object is to provide novel copper con taining solutions which function. effectively as physical, chemical and solvent transfer developers for photoproduced latent images. Other objects will become apparent hereinafter. i

In accordance with the invention, we carry out the intensification or development of photoproduced latent images in a number of ways and with practically any kind of photosensitive materials capable of producing developable latent image specks or nuclei on exposure to light or other radiations. For example, the copper developers of the invention are not only useful as physical, chemical and solvent transfer developers for the intensification or development of latent images formed by exposure of conventional gelatino-silver halide emulsion layers, but in addition also function eifectively as physical developers of latent images produced with other kinds of photosensitive materials such as any of those described in copending application of Gilman et aL, Ser. No. 244,456, filed Dec. 13, 1962, wherein the photosensitive layer comprises a light insensitive nucleating agent, e.g., particles of silver, metal sulfides, metal selenides, silver proteinates, zinc oxide, zinc hydroxide, lead iodide, etc, and a sensitizer, e.g., a light sensitive dye, a photoreactive sulfur compound, and the like, which inhibits physical development of the nuclei until exposure to light causes the nuclei to form active sites for physical development. v 0 Still other photosensitive materials that give on exposure physically developable latent images can with advantage be intensified or developed by using the copper developers of the invention, for example, photosensitive materials such as described in copending application of Gilman et al, Ser. No. 411,594, filed Nov. 16, 1964, wherein the photographic element comprises a light-sensitive layer containing a silver complex of a conventional sensitizing dye and having sensitivity only in the region of absorption by the silver-dye complex and which on exposure to radiation form active sites for physical development.

The copper developers of the invention can-be used, as previously-indicated, as physical, chemical and solvent transfer developers. When used as -solvent transfer developers, a solvent for silver halide is also incorporated in the developer composition. A particularly useful copper developer for carrying out the physical and chemical development procedures of the invention has the following formulation:

Cupric nitrate g 25-100 Ascorbic acid g 20-80 Z-aminoethanol ml 50-200 Sodium sulfite g 25-100 Water to make a total of 1 liter.

placed, if desired, by any other reducing agenttor cupric salts preferably by an alkali metal salt of ascorbic acid, e.g., sodium ascorbate, etc. The Z-aminoethanol component acts to control the alkalinity and also functions as a complexing agent for the vcupric salt. If desired it canbe replaced with other water-soluble amines such as any other aminoalkanol containing from 2 to 4 carbon atoms, e.g., propanolamine, butanolamine, diethanolamine, etc., primary, secondary or tertiary amines, e,-.g., methylamine, ethylamine, butylamine, diethylamine, triethylamine, piperidine, pyridine, etc., alkane diamines, e.g., ethylenediamine, 1,3- pr opanediamine, -1,2-propanediamine, etc., sodiumfsalt of. ethylenediamine tetraacetic acid, or with a. sulfur dioxide-amine adduct, e.g., methylaminoethanol-sQ methylaminopropanol-So etc., and the like. The sodium. sulfite component acts primarily as an antioxidant and can be substituted by a like amount of other alkalimetal sulfites, e.g., lithium sulfite, potassium sulfite, etc., or ,with ammonium sulfite. However, it will be understood-that the cupric salt and the reducing agent are critical components in the above formulation, and that the preferred combination. is cupricfnitrateand ascorbic acid. For carrying out the solvent transfer procedure of the invention, the above formulation zisv modified by the addition of about from 5 to 20 grams of a compound which is a solvent for silver halides, e.g., alkali metal thiosulfates, ammonium thiosulfates. an alkali metal thiocyanate, ammonium thiocyamate, and the like. In this case, the preferred combination includes cupric nitrate, ascorbic acid and sodium thiosulfate.

Suitable unexposed photographic films or papers for carrying out the solvent transfer development procedure of the invention include any of the conventional photographic materials comprising a suitable film support material, e.g., cellulose esters such as cellulose nitrate, cellulose acetate, cellulose acetate-propionate, etc., polystyrene, polyesters, such as polyethylene terephthalate, etc., polyethylene, polyamides, paper, glass, metal, and the like, having thereon a gelatino silver halide developing-out emulsion layer, e.g., gelatino silver chloride, -chlorobromide, -chloroiodide, -chlorobromoiodide, -bromide and -bromoiodide. However, similar materials wherein the gelatin is replaced with other carriers such as, for example, collodion, albumin, polyvinyl alcohol, polyvinyl pyrrolidone, etc., can also be used effectively. The emulsion layers can also contain sensitizers or other addenda for improving the character of the emulsion layer as is well known in the art. Emulsions of the above kind can be prepared according to known methods, for example, such as those described in Hewitson and McClintock, US. Pat. No.- 2', 61'8,556, issued Nov. 18, 1952.

The following examples will serve to illustrate" further the manner of practicing our invention.

EXAMPLE 1 This example illustrates physical development of photoproduced nuclei originating from exposure of a photosensitive layer containing a silver complex of a sensitiz ing dye.

Under .safelight conditions a light-sensitive emulsion and coating thereof were prepared in the following manner;

In a total of 380 ml. is contained:

6 ml. of formaldehyde 150 grams of 10% gelatin 12 ml. of 7 /2% saponin solution 6 ml. of 0.1 N silver nitrate 2.5 ml. of methyl alcohol solution, containing 2.5 milligrams of the. dye, l-ethyl-S-[(3-ethyl-2(3H)-benzoxazolylidene) ethylidene]-3-n-heptyl-2-thiohydantoin.

This mixture was then coated 10 grams per square foot onto a cellulose triacetate film support.

After drying the above prepared photosensitive film, it was exposed to a Kodak Model sensitometer and the exposed film then developed by a 20-second immersion in a copper developer to produce a visible negative image containing 99.7 mg. of copper per square foot in the maximum density areas The copper developer used' in the above procedui'e'had the following composition:

Water to make to a total ofl liter.

The exact proportions are not critical, but best results are obtained if the components are added in the above order. Preferably the cupric nitrate is first dissolved in water and to this are then added the other components.

By extending the time of development in the above copper developer II to minutes, high neutral density images of 1.40 are obtained by a selective deposition of copper metal on the photoproduced nuclei of the coating. Copper analyses of these sensitometric strips indicate that over milligrams of copper per square foot may be deposited on the image areas.

' EXAMPLE 2 Post-fixation physical development by the process of the invention to produce visible images with imagewise exposed conventional silver halide layers is illustrated by this example.

'An image exposure was made on Kodak Azo F-2 paper (a photosensitive paper having a conventional silver 'halide layer thereon). Half of the paper was developed for one minute in a 1:1 ratio of water and developer solution of the following composition:

The whole layer was then fixed for two minutes and washed withwater. The fixing bath had' the following composition:

Sodium thiosulfate .(pentahydrate) g 240.0 Sodium sulfite (desiccated) g .15.0 Acetic acid, 28% cc 48.0 Boric acid (crystals) g 7.5 Potassium alum g 15.0

Water to makef'a total of 1 liter.

The paper'was then cut in halfand the undeveloped,

V fixed part'of one-half was'immer'sed in the copper developer II ofabove Example 1 for 30 seconds; The dudeveloped, fixed part'of the remaining half was immersed in a 1:1 ratio of water and developersolution of the above composition III for a period of 2 minutes. The

' developer of above composition III in the fixed area.

' EXAMPLE 3 This example illustrates that besides being an excellent and rapidly working physical developer, the copper solutions of the invention represented by composition II of abov e Example I'are also extremely active chemical developers for intensifying latent images in conventional silver halide emulsion layers.

A sensitometric comparison of a two minute development in 1:2 water and conventional developer of composition .III of above Example 2 with a 20-second development in the copper developer of composition II of above Example 1 was made using a conventional microfile film and a conventional silver halide film. Analyses of the sensitometric strips processed with the copper developer indicate both copper and silver are developed in the image areas. Also, the copper developed images show comparable uniform densities over the exposure range with those developed with the conventional developer.

EXAMPLE 4 This example illustrates that the usefulness of the copper developers of the invention can be extended to solvent transfer processes by the inclusion of a silver halide solvent in the developer formulation. i

A processing web material containing a mixture of nickel and silver nuclei was prepared as follows:

(1) A nickel sulfide dispersion was produced by adding 19 cc. of 1.0 N sodium sulfide to a precipitation vessel containing 50 grams of i 10 percent gelatin solution and 1435 cc. of water at a pH of. about 5.7 and a temperature of about 104 F. About seconds after the addition of the sodium sulfide solution, -a solution containing 20.8 cc. of- 1.0 N nickelous nitrate and 535 cc. of water was dumped into the reaction mixture over a period of seconds with rapid mechanical agitation. At the end of the addition, the mixture was stirred for 30 seconds at 104 F. Four hundred fifty grams of a 10 percent gelatin solution was then added and the dispersion obtained stirred at 104 F. for an additional minutes. i

(2) A silver iodide dispersion was prepared as in above (1) except that potassium iodide was substituted for the sodiumsulfide and silver nitrate was substituted for the nickelous nitrate. f

(3) A coating dispersion was prepared by mixing together 500 grams of the nickel sulfide dispersion of above (1), 100 grams of the silver iodide dispersion of above (2), 380 grams of a 10 percent gelatin solution and 1783 cc. distilled water. To this dispersion, whilestirring at 104 F., was added 30 cc. as a' 1 percent solution in methanol of l-methyl-l,2,3,6-tetrahydro-4-thiol, 60 cc. as a 1 percent solution inmethanol of 3- mercapto-l,2,4-triazole, and 44 cc. as a 10 percent solution in distilled water of 3,8-dithiodecane-1,10 bis (N methyl piperidinium-ptoluene sulfonate). To this was added a coating aid and 90 cc. of a 10 percent formaldehyde solution as a hardener. The dispersion thus obtained Was then coated on white pigmented cellulose acetate sheet at a coverage to yield 82.5 mg. gelatin per square foot. t

The coated cellulose acetate receiving sheet prepared as above described was soaked for 30 seconds in a copper developer of the following composition:

Cupric nitrate g 50 Ascorbic acid ;g 40 Z-aminoethanol ml..- 100 Sodium sulfite g 50 Sodium thiosulfate pentahydrate -g Water to make a total of 1 liter.

EXAMPLE 5 n The copper physical developers of the invention can also be used to develop latent images produced in zinc hydroxide photosensitive layers as illustrated in this example.

The zinc hydroxide coating emulsion was prepared by the following steps: I

(1) To 1300. ml. of distilled water add 300 g. of ZI1(NO3)26H2O- i (2) To 600 ml. of distilled water add g. of sodium hydroxide.

(3) Add (2) to (1) under a 1A safelight over a five minute period with constant stirring.

(4) Wash the resulting precipitate by decantation at least five times. i

(5) Mix the washed precipitate (10% solids) with equal volume of 10% gelatin. 1

(6) Run mixture through a colloid mill set at..006". (7) For coating, add to ml. of the above preparation (a) 3 ml. of a 7 /2 saponin solution (b) 0.5 ml. of 10% formaldehyde.

The above emulsion was then coated on a titanium dioxide pigmented cellulose acetate support and the coating dried. This photosensitive material was nextexposed imagewise, dipped in a 1% aqueous silver nitrate solution for 5 seconds rinsed with water for 20 seconds, and then immersed in the copper developer of composition II of Example 1 for a period of 5 minutes to obtain a dense uniform image in the areas of exposure. i

EXAMPLE 6 This example illustrates the physical development of latent images produced in lead iodide photosensitive layers with the copper developers of the invention.

The lead iodide coating emulsion was prepared by the following steps:

(1) Dissolve 30 g. of lead nitrate in 300 ml. of distilled water.

(2) Dissolve 33 g. of potassium iodide in 300 ml of distilled water.

(3) Add (2) and (1) with stirring, allow precipitate to settle, then wash by decantation.

(4) Add 500 ml. of water to the above washed precipitate, then to 50 ml. of this slurry add 100 ml. of ten percent gelatin, 3 ml. of 7 /2% Saponin solution, 0.5 1111.015 10% formaldehyde, and 0.5 ml. of 11% thioacetamide solution.

The above emulsion was then coated 0.005 inch wet thickness on a suitable cellulose acetate support. The dry coating was exposed imagewise, dipped in a 1% aqueous silver nitrate solution for 5 seconds, rinsed with water for 20 seconds, and then immersed in a copper developer of composition II of above Example 1 for 1-5 seconds to obtain a dense photographic image in the area of exposure.

' EXAMPLE 7 This example illustrates the physical development of latent images produced in methylene blue type of photosensitive layers with the copper developers of the invention.

The methylene blue coating emulsion was prepared by steps as follows:

To 100 ml. of 10% bone gelatin add:

(1 '100 ml. of distilled water (2) 5 ml. of a 7 /2 saponin solution (3) 3 ml of a 10% aqueous formaldehyde solution seconds to obtain a dense photographic image in the ex-- posed areas.

By following the procedures of the above examples, latent images produced with any other of the photosensitive materials previously mentioned as being suitable can be effectively intensified by using the copper developers of the invention in the specified manner as physical, chemical and solvent transfer developers.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood-that variations and modifications can be effected within the spirit and scope of the invention' as described hereinabove' and as defined in the appended claims.

We claim:

- 1. A process'for the intensification of photoproduced developable latent image nuclei in an exposed photosensitive layer selected from the class consisting of silver halide, zinc hydroxide, lead iodide, methylene blue and silver-dye complex layers comprising contacting said layer with an aqueous developing solution comprising a cupric saltand a reducing agent for said cupric salt selected from the class consisting of ascorbic acid and salts of ascorbic acid.

- 2. A process for the intensification of photoproduced developable latent image nuclei in an exposed photosensitive layer comprising contacting said layer with an aqueous developing solution comprising cupric nitrate and ascorbic acid.

3. A process for the intensification of photoproduced developable latent image nuclei in an exposed silver halide photosensitive layer comprising contacting said layer With an aqueous developing solution comprising a cupric salt and an ascorbic acid reducing agent.

4. A process of claim 3 wherein said latent image is contacted with said developing solution after the unexposed silver halide has been removed in a fixing bath.

5. A process for the intensification of photoproduced latent image nuclei in an exposed photosensitive zinc hydroxide emulsion layer comprising contacting said layer with an aqueous developing solution comprising a cupric salt and an ascorbic acid reducing agent.

6. A process for the intensification of photoproduced latent image nuclei in an exposed photosensitive lead iodide emulsion layer comprising contacting said layer with an aqueous developing solution comprising a cupric salt and an ascorbicacid reducing agent. I

7. A process forthe intensification of photoproduced latentimage nuclei in an exposed photosensitive methylene blue emulsion layer comprising contacting said layer with an aqueous developing solution comprising a cupric salt and an ascorbic acid reducing agent.

8. A process for the intensification of photoproduced latent image nuclei in an exposed silver-dye complex emulsion layer comprising contacting said layer with an aqueous developing solution comprising a cupric salt and an ascorbic acid reducing agent.

9. A process for the intensification of photoproduced developable latent image nuclei in an exposed photosensitive layer comprising contacting said layer with an aqueous developing solution comprising a cupric salt and a reducing agent for said cupric salt selected from the class consisting of ascorbic. acid and ascorbic acid salts.

10. A photographic material produced by the process of claim 9.

11. The method of amplifying a metallic image of a metal at least as noble as copper, which method comprises contacting a physically developable copy medium comprising said metallic image with ascorbic acid and cupric ion to deposit selectively metallic copper in image areas of said copy medium Where metal is already present.

12. The method as in claim 11 wherein said metallic image comprises silver.

13. The method as in claim 11 wherein a water soluble. amine is additionally present with said ascorbic acid and said cupric ion.

14. A solvent transfer process for the intensification- 8 of latent layer comprising (a) contacting said layer with an aqueous developing solution comprising a cupricsalt, an ascorbic acid reducing agent and a solvent for silver halide,and (b) then contacting said layer while still wet with said developing solution with a silver precipitating receiving sheet.

15. A process of claim 14 wherein said cupric salt is cupric nitrate, said reducing agent is ascorbic acid and said silver halide solvent is sodium thiosulfate.

16. A photographic material produced by the process of claim 14. Y i

17. The method of amplifying a latent metallic image in a copy medium which comprises contacting a copy medium comprising a latent metallic image with a developer comprising ascorbic acid and cupric ion to deposit selectively metallic copperin areas containing the latent image. r 18. A process as in claim 17 wherein the latent metallic image is produced by exposing acopy medium'comprising photosensitive silver halide. Y

19. The method as in claim 17 wherein said: metallic image-comprises silver, zinc'and lead.

20. The; method as-in claim 17 .wherein said latent metallic image comprises metallic silver..

-21. The method as inwclaim 19 wherein said latent metallic image comprises metallic zinc. I

.22. A process as in claiml'T-wherein the latent metallic image is produced by .exposinga photosensitive medium comprising zinc oxide.

23. The method as in claim 19 wherein said medium is contacted with cupric ion, ascorbic acid and a water soluble amine. v

24. In the method of image reproduction which cornprises exposing a copy medium to activating radiation said copy medium comprising a photosensitive material rendered capable, by exposure to said radiation, of reducing silver ion to metallic silver on contact, and contacting said exposed medium to silver ion prior to, at the time of, or subsequent to the exposure step to form a latent image of'metallic silver in said copy medium, the improvement wherein said latent silver image is amplified and made visible by contact of said medium. with latent ascorbic acid and cupric ion.

25. A developed'copy medium having'avisible image therein, said medium comprising a carrier and an image formed therein by a first metallic latent silver image a second, heavier, visible overlying metallic copper image.

26. A copy medium as in claim 2 5wherein'the copy medium'compris'es at'least one member selected from the group consisting of silver halide and a photoconductor.

27. A developed photosensitive copy medium comprising a carrier and a visible imagecomp'rising a first latent image of silver','zin'c 'or'lead and a second,'=heavier, visible overlying metallic copper image. 1 i

28. An aqueous solution of the formula? I Cupric nitrate "g 25 Ascorbic acid g 20-80 2 -Aminoethanol ml .-5020O Sodium sulfite g 25-100 Water to make a total of 1 liter.

29. An aqueous solution effective for the intensification of photoproduced latent images by a solvent transfer method comprising a cupric salt, an ascorbic acid, re* ducing agent for said cupric salt and a solvent for silver halides v 30. An aqueous solution of claim 29 wherein 'said cupric'salt is selected fromthe group consisting of cupric chloride, cupric bromide, cupric nitrate," cupric sulfate, cupric acetate, cupric benzoate, and cupric lactate, said reducing agent is selected from the group consisting of ascorbic acid and an alkali metal salt of ascorbic acid, and said solvent for silver halideais selected-from the group consisting of an alkali metal-1 thiosulfate, ammonium thiosulfate, an alkali metal thiocyanate and am monium thiocyanate.

9 10 31. An aqueous solution of the formula: 3,4 6,619 5/ 1969 Gi man 9 2,751,300 6/1956 James et al. 96-29 Cupric nitrate g 25-100 2,854,386 9/ 1958 Lyman et a1. 9660 Ascorbic acid g 20-80 3,152,903 10/1964 Shepard et al. 9664 2-Aminoethanol ml 50-200 Sodium sulfite g 25-100 5 FOREIGN PATENTS Sodium thiosulfate pentahydrate -g 5-20 7 5 5 19 4 Belgium 9 4 PD Water to make a total of 1 liter.

32. A composition for the amplification of images OTHER REFERENCES formed in a copy medium by the presence therein of a metal, which composition comprises a solution of cupric ion, an acid acceptor, and ascorbic acid in a common solvent and wherein the acid acceptor is an organic amine.

10 Chemical Abstract 52: 16021c of Neiadas et aL,

Compt. Rend. 246-, 2543-5 (1958).

Focal Encyclopedia, vol. 1, pp. 432-3, 1965.

References Cited NORMAN G. TORCH'IN, Primary Examiner UNITED STATES PATENTS 15 M. F. KELLEY, Assistant Examiner 3,512,972 5/1970 Case 96-48 U.S. Cl. X.R. 2,543,181 2/1957 Land 96-76 96-50, 60, 114.6 

